mysql - 通过 MySQL InnoDB 行锁的应用程序互斥

Question

我的应用程序由几个 Apache 服务器组成，这些服务器与一个通用的 MySQL 框通信。该应用程序的一部分允许用户在未来创建一小时的约会。我需要一种机制来防止不同的用户同时来自不同的 Apache 实例，预订相同的一小时预约时段。我已经看到在 Oracle 数据库上实现了类似的“系统间互斥”解决方案(基本上是“选择...更新”)，但还没有处理对 MySQL 执行相同操作的细节。将不胜感激任何建议、代码或文档引用、最佳实践等。确实尝试谷歌搜索，但主要是关于 MySQL 内部互斥锁的讨论。

这些是我认为相关的我的 MySQL 设置(我的代码将有 try-catch 和所有并且在不解锁它锁定的内容的情况下永远不会放弃，但也必须考虑在这些情况下发生的情况):

mysql> show variables like 'innodb_rollback_on_timeout';
+----------------------------+-------+
| Variable_name              | Value |
+----------------------------+-------+
| innodb_rollback_on_timeout | OFF   | 
+----------------------------+-------+
1 row in set (0.00 sec)

mysql> show variables like 'innodb_lock_wait_timeout';
+--------------------------+-------+
| Variable_name            | Value |
+--------------------------+-------+
| innodb_lock_wait_timeout | 100   | 
+--------------------------+-------+
1 row in set (0.00 sec)

mysql> select @@autocommit;
+--------------+
| @@autocommit |
+--------------+
|            1 | 
+--------------+
1 row in set (0.00 sec)

您可以推荐任何替代解决方案(MySQL 之外)？我也有一个正在运行的 memcached 实例，但经常被刷新(并且不确定我是否想要 memcachedb 等来实现容错)。

感谢您的帮助...

Answer 1

还可以使用 MySQL 和 MariaDB 的GET_LOCK(和RELEASE_LOCK)函数:

• https://dev.mysql.com/doc/refman/5.5/en/miscellaneous-functions.html#function_get-lock(过时的链接)
• https://dev.mysql.com/doc/refman/8.0/en/locking-functions.html#function_get-lock
• https://mariadb.com/kb/en/library/get_lock/

这些函数可用于实现问题中描述的行为。

---

获取锁 my_app_lock_1。

SELECT GET_LOCK('my_app_lock_1', 1000); -- lock's name 'my_app_lock_1', timeout 1000 ms
+---------------------------------+
| GET_LOCK('my_app_lock_1', 1000) |
+---------------------------------+
|                               1 |
+---------------------------------+

释放锁:

DO RELEASE_LOCK('my_app_lock_1'); -- DO makes a result set ignored

---

请注意(引自 MariaDB 的文档):

• >

  Names are locked on a server-wide basis. If a name has been locked by one client, GET_LOCK() blocks any request by another client for a lock with the same name. This allows clients that agree on a given lock name to use the name to perform cooperative advisory locking. But be aware that it also allows a client that is not among the set of cooperating clients to lock a name, either inadvertently or deliberately, and thus prevent any of the cooperating clients from locking that name. One way to reduce the likelihood of this is to use lock names that are database-specific or application-specific. For example, use lock names of the form db_name.str or app_name.str.

• >

  Locks obtained with GET_LOCK() do not interact with transactions.